This invention relates to slide projectors, and has particular reference to slide projectors of the type in which slides in a flexible magazine are swung one by one into and out of a slide-projection station or filmgate, about an axis extending along one side edge of the slide and positioned along one side of the filmgate.
One slide projector of this general type, shown in U.S. Pat. No. 3,729,254, is of the belt type in which a plurality of slides are held in a magazine comprising an endless flexible belt with a series of slide-holding elements in the form of metal clips mounted on its outer side. This belttype magazine is fitted around two parallel shafts, one alongside the slide-projection station, and is driven step by step by turning of one of the shafts through 90.degree. increments. A functionally similar flexible magazine of more recent development, mounts an endless series of slide-holding elements, preferably molded plastic parts, individually and slidably on track defining an endless path that may be virtually the same in shape as the slide path in a belt-type projector.
In magazines of both of these types, slides moving into and out of the projection station swing through a tight arc of approximately 90.degree., typically about the axis of the drive shaft, and along a U-shaped section of track in the track-type projector. Such arcuate swinging movement feeds each slide into the projection station, in which the slide is positioned across the optical axis of the projector, in line with the various lenses and the light source. This is to be contrasted with the movement of slides in more conventional projectors in which slides held in a rigid magazine, whether straight or annular, are shifted edgewise out of the magazine for projection, and then are returned to the magazine for indexing movement.
The advantages of flexible-magazine projectors now are well known, and include, among others, smooth and rapid slide changing, as fast as four or more per second, jam-free operation, and compact slide storage. One disadvantage of past configurations, however, has been the distance that the condensing lens must be maintained from the slide-projection station, to permit the slides to swing into and out of the station. Because of the length of the slides, the condensing lens has had to be spaced a considerable distance behind the station, to be out of the arc of slide movement.
As a result of this distance, it has been necessary to use relatively large and expensive condensing lenses in order to project slides with acceptable brightness and high quality. Efforts have been made to minimize the lens size and cost with specially designed lenses, but as far as is presently known, these efforts have not solved the problem satisfactorily.
The principal objective of this invention is, therefore, the provision of a unique slide projector of the flexible-magazine type in which a conventional lens may be disposed in the optimum position for projection purposes, without detracting from, or interfering with, the operation of the projector.